The calcium and zinc salts of diethylenetriamine penta-acetate (Ca-DTPA and Zn-DTPA) have been approved by the Food and Drug Administration for the decoporation, removal or elimination of known or suspected internal contamination of humans with the transuranic metals (Z>92), plutonium, americium and curium. More specifically Ca-DTPA and Zn-DTPA are chelating agents that work by binding and holding onto radioactive materials or certain other poisons that enter the body. Once bound to the radioactive material or poison, the chelating agent is then passed from the body in the urine and or feces. The chelating agents help decrease the amount of time it takes to get the poison out of the body.
Ca-DTPA and Zn-DTPA are not absorbed from the GI tract to any appreciable extent and therefore must be administered by (1) subcutaneous injection directly into a vein, (2) intravenously by dripping into a vein from a bag or (3) by nebulized inhalation by means of a mist or spray breathed into the lungs.
A need exists for the development of a form of diethylene triamine penta-acetic acid (DTPA) that can be administered orally for use in the possible event of a massive radiation poisoning emergency such as could occur by the detonation of a dirty bomb by terrorists or inadvertent release of radioactivity into a work place or the environment. The present invention relates to pharmaceutical compositions and treatment methods meeting this need. More specifically, esters and amides of DTPA have been developed that are readily absorbed following oral administration and are subsequently and rapidly hydrolyzed back to active DTPA by esterases or amidases normally present in the intestinal lumen, liver and/or blood.